Widevine Initialization Fails with NotSupportedError in Electron 35.1.5+wvcus

[interconsolutions]

I'm developing an Electron-based macOS application that uses Widevine CDM to play DRM-protected videos. Despite correctly configuring the Widevine CDM files and entitlements, the Widevine initialization fails with NotSupportedError: Unsupported keySystem or supportedConfigurations, preventing video playback.

I'm using Electron 35.1.5+wvcus (Chromium 134) with Widevine CDM 4.10.2891.0, which is marked as supported in your compatibility table (Electron Releases). The Widevine files are correctly detected, and the signature is verified, but the initialization fails.

Environment

Electron Version: 35.1.5+wvcus (Chromium 134)
Widevine CDM Version: 4.10.2891.0
OS: macOS (ARM64)
Node.js Version: 20.10.0
electron-builder Version: 26.0.12

Steps to Reproduce

Set up an Electron app with the following package.json dependencies:
"devDependencies": {
"@castlabs/electron-releases": "https://github.com/castlabs/electron-releases#v35.1.5+wvcus",
"electron": "github:castlabs/electron-releases#v35.1.5+wvcus",
...
}

Place Widevine CDM 4.10.2891.0 files in WidevineCdm/4.10.2891.0/ with the structure:
WidevineCdm/
└── 4.10.2891.0/
├── manifest.json
└── _platform_specific/
└── mac_arm64/
├── libwidevinecdm.dylib
└── libwidevinecdm.dylib.sig

Configure electron-builder to copy WidevineCdm to Contents/Resources/WidevineCdm:
"extraResources": [
{
"from": "WidevineCdm",
"to": "WidevineCdm"
}
]

Set macOS entitlements in entitlements.mac.plist:
com.apple.security.cs.allow-unsigned-executable-memory

com.apple.security.cs.allow-jit

com.apple.security.cs.allow-dyld-environment-variables

com.apple.security.cs.disable-library-validation

com.apple.security.temporary-exception.mach-lookup.global-name

com.apple.widevinecdm

In main.js, configure Widevine and attempt initialization:
const widevineDir = process.env.NODE_ENV === 'development'
? path.join(app.getPath('userData'), 'WidevineCdm')
: path.join(path.dirname(app.getPath('exe')), '..', 'Resources', 'WidevineCdm');
app.commandLine.appendSwitch('widevine-cdm-path', widevineDir);
app.commandLine.appendSwitch('widevine-cdm-version', '4.10.2891.0');
mainWindow.webContents.executeJavaScript(navigator.requestMediaKeySystemAccess("com.widevine.alpha", [{ initDataTypes: ["cenc"], videoCapabilities: [{ contentType: "video/mp4; codecs=\\"avc1.64001E\\"", robustness: "" }], audioCapabilities: [{ contentType: "audio/mp4; codecs=\\"mp4a.40.2\\"", robustness: "" }], persistentState: "optional", sessionTypes: ["temporary"] }]).then((mediaKeySystemAccess) => { console.log('✅ Widevine initialized!'); }).catch((err) => { console.error('❌ Failed to initialize Widevine:', err.name, err.message); }););

Build and run the app, then attempt to play a DRM-protected video.

Expected Behavior
Widevine CDM should initialize successfully, allowing DRM-protected videos to play on sites without the error "Ihr Browser unterstützt diesen Medientyp nicht."

Actual Behavior
Widevine initialization fails with:
❌ Failed to initialize Widevine: NotSupportedError Unsupported keySystem or supportedConfigurations.

It displays the error indicating DRM is not enabled.

Steps Tried

Verified Widevine Files:

Confirmed WidevineCdm/4.10.2891.0/ contains manifest.json, libwidevinecdm.dylib, and libwidevinecdm.dylib.sig.
Signature verification passes (main.js: Widevine CDM signature verified).
Inspected manifest.json to ensure it includes avc1, mp4a, cenc, and robustness levels like SW_SECURE_CRYPTO.

Updated Widevine Configuration:

Tried alternative codecs (avc1.4d401e, avc1.42e01e) and robustness levels (SW_SECURE_CRYPTO, HW_SECURE_ALL):
navigator.requestMediaKeySystemAccess("com.widevine.alpha", [
{
initDataTypes: ["cenc"],
videoCapabilities: [{
contentType: "video/mp4; codecs=\"avc1.4d401e\"",
robustness: "SW_SECURE_CRYPTO"
}],
audioCapabilities: [{
contentType: "audio/mp4; codecs=\"mp4a.40.2\"",
robustness: "SW_SECURE_CRYPTO"
}],
persistentState: "optional",
sessionTypes: ["temporary"]
},
{
initDataTypes: ["cenc"],
videoCapabilities: [{
contentType: "video/mp4; codecs=\"avc1.42e01e\"",
robustness: "HW_SECURE_ALL"
}],
audioCapabilities: [{
contentType: "audio/mp4; codecs=\"mp4a.40.2\"",
robustness: "HW_SECURE_ALL"
}],
persistentState: "optional",
sessionTypes: ["temporary"]
},
{
initDataTypes: ["cenc"],
videoCapabilities: [{
contentType: "video/mp4",
robustness: ""
}],
audioCapabilities: [{
contentType: "audio/mp4",
robustness: ""
}],
persistentState: "optional",
sessionTypes: ["temporary"]
}
])

Still received NotSupportedError.

Checked Entitlements:

Confirmed entitlements.mac.plist includes all necessary Widevine permissions, including com.apple.widevinecdm.

Spoofed User Agent:

Set user agent to mimic Chrome:
app.userAgentFallback = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36';

Applied to both BrowserWindow and BrowserView.

Disabled WebRTC:

Added --disable-features=WebRTC to prevent browser fingerprinting.

Reviewed Network and Session Issues:

Ensured stable internet connection.
Noted that browserViewManager.js loads without session data, but authentication appears to work for page loading.

Checked Build Configuration:

Verified package.json and electron-builder settings to ensure Widevine files are correctly copied and no build flags disable DRM.

Questions

Are there known issues with Widevine CDM 4.10.2891.0 and Electron 35.1.5+wvcus (Chromium 134) that could cause NotSupportedError?
Does the +wvcus build require specific navigator.requestMediaKeySystemAccess configurations (e.g., codecs, robustness levels) ?
Are there additional entitlements or command-line switches needed for Widevine in Electron 35.x?
Could BrowserView configuration affect Widevine initialization? If so, what webPreferences are required?
Is there a recommended Widevine configuration video playback with this setup?

Additional Information

The app uses BrowserView to load pages, with browserViewManager.js handling session data and API request blocking. videos fail with the DRM error, suggesting Widevine is not fully enabled.
The manifest.json includes avc1, mp4a, cenc, and robustness levels like SW_SECURE_CRYPTO and HW_SECURE_ALL.
Logs confirm Widevine files are detected and signed correctly.

Any guidance on resolving the NotSupportedError or enabling Widevine for video playback would be greatly appreciated!

[khwaaj]

You should not download and copy the Widevine CDM files on your own, ECS will use the Component Updater to install the CDM by itself (assuming you are using things correctly). Bundling the CDM is not recommended (or supported) since it has legal implications. Also, the widevine-cdm-path and widevine-cdm-version are obsolete, and not supported by ECS.

The error you are seeing indicates that the CDM has not been installed/registered at all. There are two common reasons for this:

1. When you create your package with electron-builder it is actually pulling a mainline Electron release instead of ECS. To avoid this, make sure that you are setting a mirror for electron-builder to use, e.g. like here.
2. You are not waiting for the CDM to become ready before opening your browser window. To do this you need to use the components API that ECS adds, e.g. like here.

You will also need to VMP sign your package using the VMP signing service we provide, or it will not work with most commercial services. I see you mentioned signatures in your comment, but it is not clear which signatures you are talking about, so I can't say for sure if this is done correctly (and it is not the immediate problem since the CDM is not loaded at all). What needs to be done is documented on the page linked above.

About entitlements the only thing that is really required to use the CDM is com.apple.security.cs.disable-library-validation (since your app and the CDM will be signed by different entities).

Assuming all of this is done correctly you will see the same behavior as when you are using EME within Chrome.